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Semitendinosus Muscle Anatomy

Quick Overview View Flashcards
Origin
  • Ischial tuberosity
Insertion
  • Medial surface of the superior tibia
Action
  • Flexes knee
  • Extends the hip
  • Medially rotates the tibia when the knee is flexed
Innervation
  • Tibial division of the sciatic nerve (L5, S1, S2)
Blood Supply
  • Inferior gluteal artery
  • Perforating arteries
Last updated: Estimated Reading Time: 8 min

Location & Overview

The semitendinosus muscle is one of the three muscles that make up the hamstring muscle group. The other two hamstring muscles are the semimembranosus and biceps femoris muscles. The semitendinosus is the most centrally located hamstring muscle. It is located in the posterior compartment of the thigh, between the biceps femoris and semimembranosus. The semitendinosus muscle is more superficial than the semimembranosus (meaning it is located closer to the skin’s surface) and covers a large portion of the semimembranosus. The attachments of the semitendinosus are relatively close to those of the semimembranosus, which shows their close anatomical relationship.[1]

semitendinosus muscle posterior view
Here we can see the semitendinosus muscle from a posterior view.
semitendinosus muscle posterolateral view
Here we can see the semitendinosus muscle from a posterolateral view.
semitendinosus muscle lateral and medial view
Here we can see the semitendinosus muscle from a lateral and medial view. The lateral view is on the left and the medial view is on the right.
semitendinosus muscle anterolateral view
Here we can see the semitendinosus muscle from an anterolateral view.
semitendinosus muscle highlighted in red among the other muscles of the hip and thigh from a lateral and medial view
Here we can see the semitendinosus muscle highlighted in red among the other muscles of the hip and thigh, seen from a lateral and medial view. The lateral view is on the left and the medial view is on the right.
semitendinosus muscle highlighted in red among the other muscles of the hip and thigh from a posterior view
Here we can see the semitendinosus muscle highlighted in red among the other muscles of the hip and thigh, seen from a posterior view. The gluteus maximus muscle is removed from the left side of the image to show its position in relation to this muscle.
Hamstring muscles labeled from a posterior view
Pictured here are the hamstring muscles from a posterior view. The long and short heads of biceps femoris, semitendinosus, and semimembranosus are labeled.
Compartments of the thigh
Here we can see an image of the compartments of the thigh. We can see the semitendinosus in the posterior compartment, the section colored in red.

Origin & Insertion

The semitendinosus originates at the superior portion of the ischial tuberosity. The ischial tuberosity is a bony protrusion located on the posterior aspect of the ischium, which is the lower part of the hip bone. This origin point is shared with the other two hamstring muscles (semimembranosus and biceps femoris).[2,1]

The muscle then travels down the posterior and medial portion of the thigh, where it inserts below the knee joint on the medial surface of the superior part of the tibia. This insertion is part of the group of tendons known as the ‘pes anserinus,’ which includes the tendons of the semitendinosus, sartorius, and gracilis muscles.[2,1]

origin of the semitendinosus muscle highlighted in red
Here we can see the origin of the semitendinosus muscle highlighted in red. It originates at the ischial tuberosity.
insertion of the semitendinosus muscle highlighted in blue
Here we can see the insertion of the semitendinosus muscle highlighted in blue. It inserts at the medial surface of the superior tibia.

Action & Function

The semitendinosus muscle plays a role in several movements at the hip and knee joints. Its primary functions include flexing the knee joint, extending the hip joint, and medially rotating the tibia on the femur when the knee is flexed.[2,3]

Flexion of the knee joint involves bending the knee, which brings the lower leg closer to the back of the thigh. Extension of the hip joint involves moving the thigh backward relative to the hip, such as when pushing off the ground when walking.[2,3]

Furthermore, the semitendinosus muscle assists in medially (internally) rotating the tibia on the femur when the knee is flexed. This action involves turning the lower leg (tibia) inward relative to the thigh without moving the thigh itself.[2,3]

Image of a person demonstrating the movement of knee flexion.
In this image, you can see an example of knee flexion, which is the action of bending your knee. The opposite movement of knee flexion is knee extension. The semitendinosus contributes to flexion of the knee joint.
Image of a person demonstrating the movement of hip extension.
In this image, you can see an example of hip extension. Hip extension is the movement of the thigh or the upper leg backward, away from the body, in the sagittal plane. This action involves increasing the angle between the thigh and the pelvis, causing the hip joint to straighten or extend. The opposite movement of hip extension is hip flexion. The semitendinosus contributes to extension of the hip joint.
Image of a person demonstrating the movement of medial rotation of the tibia.
In this image, you can see an example of medial rotation of the tibia. Medial rotation of the tibia involves inward rotation of the shinbone toward the midline of the body. The opposite movement of medial rotation of the tibia is lateral rotation of the tibia. The semitendinosus contributes to medial rotation of the tibia when the knee is flexed.

Innervation

The semitendinosus muscle receives its innervation from the tibial division of the sciatic nerve, which arises from nerve roots L5, S1, and S2.[3] The sciatic nerve is the largest nerve in the body and provides motor and sensory functions to the lower limbs.[4]

The tibial division of the sciatic nerve supplies the motor signals necessary for the semitendinosus muscle to perform its actions, such as flexing the knee, extending the hip, and medially rotating the tibia on the femur when the knee is flexed.[3] In addition, the sciatic nerve also carries sensory information from the skin and deeper structures of the lower limb, enabling the perception of touch, pain, and temperature.[4]

sciatic nerve highlighted in red
Here we can see the sciatic nerve. Although the tibial nerve separates from the sciatic nerve just above the knee, it is important to note that the nerves in our body are organized in a network, not in a strictly linear path. The nerve fibers that will eventually form the tibial nerve are present within the sciatic nerve from the point at which it leaves the spinal cord. These fibers travel within the sciatic nerve and reach the muscles they innervate, including the proximal (top) part of the semitendinosus muscle, long before the physical branching of the tibial nerve occurs near the knee. Thus, it is still accurate to say that the semitendinosus is innervated by the tibial nerve, even though the physical branching occurs distally.
tibial nerve highlighted in red
Here we can see the tibial nerve branching off from the sciatic nerve. The tibial division of the sciatic nerve innervates the semitendinosus muscle.

Blood Supply

The blood supply to the semitendinosus muscle is provided primarily by the inferior gluteal artery and the perforating arteries. The inferior gluteal artery is a branch of the internal iliac artery, which supplies blood to the gluteal region and the posterior thigh muscles, including the hamstring muscles. The perforating arteries are branches of the deep femoral artery (profunda femoris) and perforate the adductor magnus muscle to supply blood to the posterior compartment of the thigh.[5]

References

  1. [1] Moore KL, Agur AMR, Dalley AF. Clinically Oriented Anatomy. 8th ed. Philadelphia: Lippincott Williams & Wilkins; 2017.
  2. [2] Rodgers CD, Raja A. Anatomy, Bony Pelvis and Lower Limb, Hamstring Muscle. (Updated 2021 Aug 11). In: StatPearls (Internet). Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK546688/
  3. [3] Afonso J, Rocha-Rodrigues S, Clemente FM, et al. The Hamstrings: Anatomic and Physiologic Variations and Their Potential Relationships With Injury Risk. Front Physiol. 2021;12:694604. Published 2021 Jul 7. doi:10.3389/fphys.2021.694604
  4. [4] Standring S. (2015). Gray’s Anatomy: The Anatomical Basis of Clinical Practice, 41st Edn. Amsterdam: Elsevier.
  5. [5] Tomaszewski KA, Henry BM, Vikse J, Pękala P, Roy J, Svensen M, Guay D, Hsieh WC, Loukas M, Walocha JA. Variations in the origin of the deep femoral artery: A meta-analysis. Clin Anat. 2017 Jan;30(1):106-113. doi: 10.1002/ca.22691. Epub 2016 Feb 2. PMID: 26780216.

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